Postal stamps can be printed by gravure, intaglio, offset, and flexo techniques. The official postage stamps are commonly printed using a Gravure process. The Gravure process is capable of creating images of very high resolution, beyond the capabilities of most common printers. The Gravure process is an intaglio process. It uses a depressed or sunken surface etched into a copper cylinder to create the image and the unetched surface of the cylinder represent non-printing areas. The cylinder rotates in a bath of ink and the etched area picks up the ink and transfers it to the media creating the image. Gravure printing is considered excellent for printing highly detailed marks or pictures.
The high set-up cost (including making the cylinders etc.) of the Gravure printing process makes it not economic for printing small quantities of stamps, for example, batches from about 10 to 1000. This prohibits a consumer from choosing an image and having a postage stamp created using that image. It also does not permit a consumer to choose an image from a gallery of images that have been previously approved and having a postage stamp created using that previously approved image.
The postal stamps are required to include fluorescent or phosphorescent materials for aligning the mail to the proper orientation in the mail sorting process. In the mail sorting process, as disclosed in U.S. Pat. No. 3,592,326, the mail envelopes pass through a so-called automatic facing machine in which the mail envelopes are illuminated by a UV light source (as specified by postal authority). The fluorescent or phosphorescent materials in the stamp emits in the visible wavelength (also as specified by the postal authority). The emitted fluorescent light must be detected by a detector for the mail envelope to pass through. If the fluorescent detector does not detect fluorescent or phosphorescent materials in the facing machine, the mail envelope is diverted out of the normal path of the mail and is reoriented and again passed through the facing machine to ensure that it is then properly oriented. This process can be repeated until the facing machine finally detects that the envelope is properly oriented. The automatic orientation detection and alignment significantly increase the throughput of the mail handling facilities.